Cardiac resynchronization therapy (CRT) may include delivering pacing stimuli to both ventricles, or to one ventricle, with the desired result of a coordinated mechanical contraction and ejection of blood from the ventricles to, for example, alleviate symptoms of congestive heart failure (CHF). However, due to a number of factors, such pacing may not always effectively provide CRT. For example, varying capture thresholds, pacing lead and/or electrode migration or dislodgement, or time required for appropriate signal processing may all be factors that affect the ability of pacing to effectively provide CRT to a patient.
When delivering CRT, such as by applying bi-ventricular stimulation, the confirmation that pacing stimuli have captured each paced ventricle is important in determining whether the desired benefits of CRT are, in fact, delivered to a patient. Some CRT devices incorporate bi-ventricular pacing technology with synchronized pacing in the right and left ventricles. Since the devices are implanted essentially to provide continuous bi-ventricular pacing therapy, it is important that pacing pulse stimuli cause an evoked response in each ventricle (i.e., that the stimuli capture, and cause contraction of, the ventricles).